System for restraining mouse

ABSTRACT

A system, of the present invention, for restraining a mouse includes: at least one home cage ( 10 ); a passage ( 20 ) through which the mouse ( 60 ) moves, the passage ( 20 ) having at least one first open end ( 21   a ); and a restraining device ( 50 ) which restrains the mouse by physically fixing the mouse ( 60 ), the at least one first open end of the passage ( 21   a ) being connected to the at least one home cage ( 10 ), the restraining device ( 50 ) being provided at a location on the passage ( 20 ) which location is different from the at least one first open end ( 21   a ) of the passage ( 20 ).

TECHNICAL FIELD

The present invention relates to a system for restraining a mouse usedas an experimental animal or the like.

BACKGROUND ART

Mice and rats are experimental animals that are widely used in variouskinds of research ranging from the field of basic science to the fieldof applied science. Both mice and rats have characteristics desirable asexperimental animals (e.g., both mice and rats are easy to keep and arealso high in reproductive ability). However, mice are different, in bodysize, from rats. Due to such a difference, a larger number of mice canbe kept per unit area and, indeed, a largest number of mice are kept asexperimental animals.

In recent years, mice have been growing in importance as experimentalanimals, particularly, in the field of neuroscience. An importantadvantage of mice is that more genetic manipulations can be done in micethan in any other mammals. For example, mice are widely used asexperimental animals so as to study cognition or emotion, analyze brainfunctionality, or tackle medical questions related to variousneurological diseases including neuro-degenerative diseases.

Further, in recent years, use of a fixing device which fixes the head ofan experimental animal has been becoming increasingly popular in thefield of neuroscience. Such a head fixing device plays a key role in alarge number of research topics ranging from, for example, studies ofdynamics of dendritic spines at sub-micrometer scale to studies ofdynamics of neuronal populations at millimeter scale.

CITATION LIST Non-Patent Literature [Non-Patent Literature 1]

-   Neuron. 2013 Oct. 16; 80(2):371-384

SUMMARY OF INVENTION Technical Problem

Although both mice and rats are rodents, mice are different from rats incharacteristics regarding handling. In general, rats are fairly easy tohandle and train and are relatively tolerant to restraint. Therefore, anexperiment in which the head of a rat is restrained with use of a headfixing device is relatively easily carried out, and even self-restraintto the head fixing device is relatively easily realized (Non-patentliterature 1). On the other hand, mice are extremely scared of humansand are, therefore, difficult to handle or restrain, especially,difficult to handle or restrain in an experiment in which a head fixingdevice is used.

One of advantages of use of mice is, as described above, thathigh-throughput experiments can be carried out while a large number ofmice are being kept. However, in experiments in which mice need to berestrained with use of restraining means such as a head fixing device,difficulty in restraining the mice is a big obstacle to achievement ofhigh-throughput experiments. Still more, it has not been realized torestrain mice substantially without human interaction.

The present invention has been made in view of the above problems, andan object of the present invention is to realize a novel system for amouse, the system being capable of (1) self-head restraining, (2)high-throughput, (3) automated behavioral training, (4) flexibility formany diverse training tasks, and (5) compatibility with cutting-edgeoptical technologies for brain studies (e.g. two-photon imaging,optogenetics). Another object of the present invention is to realize anovel system capable of restraining a mouse substantially without humaninteraction.

Solution to Problem

In order to attain the objects, the present invention includes at leastone of the following aspects.

1) A system for restraining a mouse, comprising:

at least one home cage for keeping the mouse therein;

a passage through which the mouse moves, the passage having at least onefirst open end; and

a restraining device which restrains the mouse by physically fixing themouse,

the at least one first open end of the passage being connected to the atleast one home cage,

the restraining device being provided at a location on the passage whichlocation is different from the at least one first open end of thepassage.

2) The system described in 1), wherein the restraining device restrainsthe mouse by physically fixing a head plate with which the head of themouse is equipped.

3) The system described in 2), further comprising a guide section whichguides the head plate, the guide section being provided to the passageand having a part inclined upward or downward as extending toward therestraining device.

4) The system described in any one of 1) through 3), wherein: thepassage has a second open end which is different from the at least onefirst open end; and the restraining device is provided on asecond-open-end side of the passage.

5) The system described in any one of 1) through 4), further comprisinga door which can be opened and closed, the door dividing an inner spaceof the passage into a first-open-end-side space and arestraining-device-side space in a case where the door is closed.

6) The system described in any one of 1) through 5), further comprisinga sensor which detects a position of the mouse being inside the passage.

7) The system described in 6), wherein operation of the restrainingdevice and/or operation of a/the door are/is automatically controlled inaccordance with information on the position of the mouse, data of whichposition is obtained from an output of the sensor.

8) The system described in any one of 1) through 7), further comprisingan activity data measuring device which obtains data on activity of themouse restrained by the restraining device.

9) The system described in any one of 1) through 8), further comprisinga learning device which supplies a reward to the mouse in associationwith predetermined movement of the mouse restrained by the restrainingdevice.

10) The system described in 8) or 9), further comprising a controlsection which automatically controls operation of an/the activity datameasuring device and/or operation of a/the learning device each of whichoperation is carried out with respect to the mouse restrained by therestraining device.

11) The system described in any one of 1) through 10), wherein:

the at least one first open end of the passage includes a plurality offirst open ends;

the at least one home cage includes a plurality of home cages; and

the plurality of first open ends are connected to the respectiveplurality of home cages.

Advantageous Effects of Invention

According to the present invention, it is possible to provide a novelsystem capable of relatively easily restraining a mouse.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view schematically illustrating a configuration of a systemin accordance with Embodiment 1 of the present invention.

FIG. 2 is a view schematically illustrating a configuration of a systemin accordance with Embodiment 2 of the present invention.

FIG. 3 is a view illustrating a main part of a configuration of avariation of the system in accordance with each of Embodiments 1 and 2of the present invention.

FIG. 4 is a view illustrating a main part of a configuration of a systemin accordance with Embodiment 3 of the present invention.

FIG. 5 is a view illustrating results of physiological recording andbrain imaging from a head-fixed mouse trained in the invented system,the physiological recording and the brain imaging having been carriedout in Example 1.

DESCRIPTION OF EMBODIMENTS Embodiment 1

The following description will discuss, with reference to FIG. 1, amouse restraining system in accordance with Embodiment 1 of the presentinvention.

A mouse restraining system 100 at least includes: a home cage 10 forkeeping a mouse 60 therein; a passage 20 through which the mouse 60moves; and a head plate latch (restraining device) 50 which restrainsthe mouse 60.

One or a plurality of mouse/mice 60 is/are housed in the home cage 10depending on a capacity of the home cage 10. In a case where theplurality of mice 60 are housed in the home cage 10, 20 or less mice 60,preferably 10 or less mice 60, more preferably 4 or less mice 60 are,for example, housed in the home cage 10 depending on the capacity of thehome cage 10. As necessary, equipment, such as a feeding place and atoilet, necessary to keep the mouse 60 is provided in the home cage 10.The home cage 10 has food pellets. Drinking water is possible only froma spout (water supply unit 72 (later described)) in a training system(i.e. water-controlled training paradigm).

(Passage 20)

The passage 20 is a hollow tubular structure through which the mouse 60can move (hollow rectangular-solid-shaped structure in Embodiment 1).Both ends of the passage 20 are opened (hereinafter, one of the bothends will be referred to as an open end 21 a (first open end) and theother one of the both ends will be referred to as an open end 21 b(second open end)). The passage 20 is connected to the home cage 10 sothat the mouse 60 can move from the home cage 10 to the passage 20 viathe open end 21 a. The head plate latch 50 is set in an open-end-21 bside of the passage 20. This allows the mouse 60 to move between thehead plate latch 50 and the home cage 10 through the passage 20. Across-sectional area of an inner space of the passage 20 is not limitedin particular, but preferably falls within a range of 7 cm² to 15 cm²,preferably 9 cm² to 12 cm² so that the mouse 60 easily enters thepassage 20 by choice. Further, a height at which the passage 20 isprovided is not limited in particular, but the passage 20 is provided sothat an internal lower surface of the passage 20 is located at a heightof 1 cm to 6 cm, preferably 2 cm to 4 cm from an internal lower surfaceof the home cage 10. Such a difference in height between the internallower surface of the passage 20 and the internal lower surface of thehome cage 10 prevents a plurality of mice 60 from freely entering thepassage 20 one after another.

The passage 20 is constituted by three portions, that is, a cage-sidepassage 20 a, a middle passage 20 b, and a latch-side passage 20 c.Those portions have an identical structure, except that the portions aredifferent in length from each other. The portions are concentricallyarranged and connected with each other so as to constitute a singlecontinuous passage 20. The cage-side passage 20 a and the latch-sidepassage 20 c are fixed to on an identical base. The middle passage 20 bis supported from underneath by a weight sensor 90. The cage-sidepassage 20 a has the open end 21 a, and the latch-side passage 20 c hasthe open end 21 b. Information on a weight of the mouse 60 being insidethe middle passage 20 b, which weight is measured by the weight sensor90, is supplied to a control section 91 and is used for automaticallycontrolling operation of the mouse restraining system 100.

(Automatic Gate 80)

The mouse restraining system 100 includes two automatic gates (door) 80a and 80 b (which may be collectively referred to as an automatic gate80) each of which is movable upward and downward. The automatic gate 80a is located so that the cage-side passage 20 a and the middle passage20 b are connected to each other via the automatic gate 80 a. In a casewhere the automatic gate 80 a is opened, an upper surface of theautomatic gate 80 a, an internal lower surface of the cage-side passage20 a, and an internal lower surface of the middle passage 20 b arearranged at the same level so as to constitute the internal lowersurface of the passage 20 (see a state indicated by “C” illustrated inFIG. 1). In a case where the automatic gate 80 a is closed, theautomatic gate 80 a is raised so as to be inserted between the cage-sidepassage 20 b and the middle passage 20 b. This causes the inner space ofthe passage 20 to be divided into an open-end-21 a-side space and ahead-plate-latch-50-side space (see a state indicated by “C′”illustrated in FIG. 1).

Similarly, the automatic gate 80 b is located so that the middle passage20 b and the latch-side passage 20 c are connected to each other via theautomatic gate 80 b. In a case where the automatic gate 80 b is opened,an upper surface of the automatic gate 80 b, the internal lower surfaceof the middle passage 20 b, and an internal lower surface of thelatch-side passage 20 c are arranged at the same level so as toconstitute the internal lower surface of the passage 20 (see the stateindicated by “C” illustrated in FIG. 1). In a case where the automaticgate 80 b is closed, the automatic gate 80 b is raised so as to beinserted between the middle passage 20 b and the latch-side passage 20c. This causes the inner space of the passage 20 to be divided into theopen-end-21 a-side space and the head-plate-latch-50-side space (seethat state indicated by “C′” illustrated in FIG. 1).

(Beam Sensor 22)

The mouse restraining system 100 includes a plurality of beam sensors 22each of which detects a position of the mouse 60 being inside thepassage 20. Each of the plurality of beam sensors 22 has an irradiationsource and a beam receiving device which locates at an opposite side ofthe irradiation source. The irradiation source of the each of theplurality of beam sensors 22 emits a beam toward the beam receivingdevice to detect a position of the mouse 60. A beam sensor 22 a is setnear the cage-side passage 20 a. This allows monitor of entrance of themouse 60 into the middle passage 20 b. A beam sensor 22 b is set in themiddle passage 20 b. This allows monitor of passage of the mouse 60through the middle passage 20 b. A beam sensor 22 c is set near the headplate latch 50. This allows monitor of arrival of the mouse 60 at thehead plate latch 50. Information on the position of the mouse 60, dataof which position is obtained from each output of the plurality of beamsensors 22, is supplied to the control section 91 and is used forautomatically controlling the operation of the mouse restraining system100.

(Head Plate Latch 50)

The head plate latch 50 restrains the mouse 60 by physically fixing ahead plate 60 a with which the head of the mouse 60 is equipped. A sizeof the head plate 60 a in combination with (1) a size of the passage 20,(2) a geometry of a latching mechanism, make it impossible for the mouse60 to escape from the head plate latch 50. The head plate 60 a has (i) athrough window 60 a ₁ in its middle in a longitudinal direction and (ii)recesses 60 a ₂ and 60 a ₂ at its respective both ends in thelongitudinal direction. The head plate latch 50 has, for example,downward protrusions which are shaped so as to fit to the respectiverecesses 60 a ₂ and 60 a ₂ of the head plate 60 a. In a case where thehead plate latch 50 is lowered, the protrusions fit to the respectiverecesses 60 a ₂ and 60 a ₂ of the head plate 60 a so that the mouse 60is restrained. In a case where the head plate latch 50 is raised, themouse 60 is released from restraint. In an alternative configuration,the head plate latch 50 comes into contact with a side surface of thehead plate 60 a with which the head of the mouse 60 is equipped. Thiscauses the head plate 60 a to be fixed so that the mouse 60 cannot moveback. This will be later described in detail with reference FIG. 3.

(Activity Data Measuring Device 51)

The mouse restraining system 100 further includes an activity datameasuring device 51 which obtains data on activity (activity data) ofthe mouse 60 whose head is restrained by the head plate latch 50. Theactivity data measuring device 51 can be any device that is used forvarious observations in each of which a mouse equipped with a head plateis an observation object. Examples of the activity data measuring device51 encompass: a microscope device such as an optical microscope; amacroscope device such as optical macroscope; an electroencephalographydevice; electrodes for physiological recordings; and optic fibers foroptogenetic stimulation. The activity data measuring device 51 obtains abrain wave of the mouse 60 (in a case where an electroencephalographydevice serves as the activity data measuring device 51), a microscopeimage or a macroscope image of an inside of the brain of the mouse 60(in a case where a microscope device or a macroscope device serves asthe activity data measuring device 51), or the like as the activity datavia the through window 60 a ₁ of the head plate 60 a.

(Water Supply Unit 72, Steering Wheel 71)

The mouse restraining system 100 further includes, on a side of the openend 21 b, a water supply unit (which also serves as a device whichsupplies an attractant) 72 and a steering wheel (which also serves as adevice which receives movement of the mouse 60). For example, in a casewhere the mouse 60 restrained by the head plate latch 50 makespredetermined movement (e.g., the mouse 60 rotates the steering wheel71), the water supply unit 72 supplies a predetermined amount of waterto the mouse 60. That is, the water supply unit 72 and the steeringwheel 71 function as a learning device 70 which supplies water to themouse 60 as a reward in association with the predetermined movement ofthe mouse 60 restrained by the head plate latch 50. The water supplyunit 72 supplies, as another example, a predetermined amount of water(attractant) to the mouse 60 so that the mouse 60 is attracted to thehead plate latch 50.

(Control Section 91)

The control section 91 automatically or semi-automatically controls theoperation of the mouse restraining system 100. According to the mouserestraining system 100, the control section 91 is connected, by wire orwireless, to each of the plurality of beam sensors 22, the automaticgate 80, the weight sensor 90, the head plate latch 50, the activitydata measuring device 51, the steering wheel 71, and the water supplyunit 72. The control section 91 is accordingly capable ofsupplying/receiving information to/from each of those devices. With thisconfiguration, for example, the control section 91 automaticallycontrols operation of the head plate latch 50 and/or operation of theautomatic gate 80 in accordance with the information on the position ofthe mouse 60, the data of which position is obtained from each output ofthe plurality of beam sensors 22. Alternatively, the control section 91automatically controls operation of the activity data measuring device51 and/or operation of the learning device 70 (the water supply unit 72and the steering wheel 71), each of which operation is carried out withrespect to the mouse 60 restrained by the head plate latch 50.

Note that the control section 91 can be performed by a logic circuit(hardware) provided in an integrated circuit (IC chip) or the like orcan be alternatively performed by software as executed by a CPU (CentralProcessing Unit). Further, the control section 91 can be configured suchthat (i) the control section 91 is constituted by a plurality of blocksand (ii) each of the plurality of blocks controls operation of acorresponding one of different devices (devices constituting the mouserestraining system 100).

Examples of how the control section 91 controls the operation of themouse restraining system 100 will be described below in detail. Note,however, that how the control section 91 controls the operation of themouse restraining system 100 is not limited to the examples inparticular. Such operation control allows realization of a novel systemcapable of restraining a mouse substantially without human interaction(that is, system capable of effectively restraining a mouse whilesuppressing the mouse's fear). Furthermore, by increasing the number ofmice housed in the home cage 10, it is possible to easily achieve a highthroughput experiment.

<Aspect 1> Screening of Mouse to be Guided to Head Plate Latch 50

First, the control section 91 controls operation of opening of theautomatic gates 80 a and 80 b so that the mouse 60 can freely movebetween the home cage 10 and the passage 20. In a case where the beamsensor 22 a detects entrance of the mouse 60 into the middle passage 20b, the control section 91 controls operation of closing of the automaticgates 80 a and 80 b. Then, the weight sensor 90 automatically measuresthe weight of the mouse 60 being inside the middle passage 20 b. In acase where the weight of the mouse 60, which weight has beenautomatically measured by the weight sensor 90, meets a predeterminedcriterion, the control section 91 controls the operation of the openingof the automatic gate 80 b, while controlling the automatic gate 80 a toremain closed, so that the mouse 60 can move to the head plate latch 50(to the latch side passage 20 c). In a case where the beam sensor 22 bdetects movement of the mouse 60 to the head plate latch 50, the controlsection 91 controls the operation of the closing of the automatic gate80 b again. On the other hand, in a case where the weight of the mouse60 does not meet the predetermined criterion, the control section 91controls the operation of the opening of the automatic gate 80 a, whilecontrolling the automatic gate 80 b to remain closed, so that the mouse60 can move back to the home cage 10. That is, according to Aspect 1,the control section 91 automatically controls the operation of theopening and closing of the automatic gate 80 with use of (i) theinformation on the position of the mouse 60, the data of which positionis obtained from each output of the plurality of beam sensors 22, and(ii) the information on the weight of the mouse 60, data of which weightis obtained from an output of the weight sensor 90. According to themouse restraining system 100, it is thus possible to automatically carryout screening of a mouse, to be guided to the head plate latch 50, by aweight of the mouse.

<Aspect 2> Training in Habituation to Head Plate Latch 50

First, the control section 91 controls the operation of the opening ofthe automatic gates 80 a and 80 b so that the mouse 60 can freely movebetween the home cage 10 and the passage 20. In a case where the beamsensor 22 b detects entrance of the mouse 60 into the latch-side passage20 c, the control section 91 can control the operation of the closing ofthe automatic gate 80 b or can alternatively control the operation ofthe opening of the automatic gate 80 b to remain opened. The controlsection 91 controls, as necessary, the operation of the water supplyunit 72 to continuously supply the predetermined amount of water to themouse 60 at a predetermined time (for example, a time at which the beamsensor 22 a detects the mouse 60) so that the mouse 60 is attracted tothe head plate latch 50. In a case where the beam sensor 22 c detectsmovement of the mouse 60 to a region in which the head plate latch 50can fix the head plate 60 a, the control section 91 controls theoperation of the movement of the head plate latch 50 so as to fix thehead plate 60 a. This causes the mouse 60 to be restrained so as not tomove. Note that the head plate 60 a can be softly fixed by the headplate latch 50 so that the mouse 60 becomes used to the head plate latch50. Next, after elapse of a predetermined time, the control section 91controls (i) the operation of the movement of the head plate latch 50 torelease the head plate 60 a from a fixed state and (ii) the operation ofthe opening of the automatic gates 80 a and 80 b relative to theoperation (i) so that the mouse 60 can move back to the home cage 10. Bycarrying out such control once or preferably repeatedly with respect toan identical mouse 60, it is possible to cause the mouse 60 to graduallybecome used to the head plate latch 50. In a case where a plurality ofmice 60 are kept in the home cage 10, it is possible to automaticallyand simultaneously train the plurality of mice 60 so that the pluralityof mice 60 are habituated to the head plate latch 50.

That is, according to Aspect 2, the control section 91 automaticallycontrols the operation of the opening and the closing of the automaticgate 80, water supply operation of the water supply unit 72, andfixation and release operation of the head plate latch 50 in accordancewith (i) the information on the position of the mouse 60, the data ofwhich position is obtained from each output of the plurality of beamsensors 22, and (ii) information on a interrelationship betweenoperation of one device and operation of another device (between theoperation of the head plate latch 50 and the operation of each of theautomatic gates 80 a and 80 b).

Note that a mouse to be conducted to the habituation training can beautomatically selected by a weight of the mouse with use of the methoddescribed in <Aspect 1>.

<Aspect 3> Learning Training—Obtainment of Data on Activity of Mouse

First, the control section 91 controls the operation of the opening ofthe automatic gates 80 a and 80 b so that the mouse 60 can freely movebetween the home cage 10 and the passage 20. In a case where the beamsensor 22 b detects entrance of the mouse 60 into the latch-side passage20 c, the control section 91 preferably controls the operation of theclosing of the automatic gate 80 b. In a case where the beam sensor 22 cdetects movement of the mouse 60 into the region in which the head platelatch 50 can fix the head plate 60 a, the control section 91 controlsthe operation of the movement of the head plate latch 50 so as to fixthe head plate 60 a. This causes the mouse 60 to be restrained so as notto move. Note that the head plate 60 a can be softly fixed by the headplate latch 50 so that the mouse 60 becomes used to the head plate latch50. The water supply unit 72 and the steering wheel 71 constitute thelearning device 70. In a case where the mouse 60 restrained by the headplate latch 50 makes the predetermined movement, for example, rotatesthe steering wheel 71, the control section 91 controls the operation ofthe water supply unit 72 to supply water (reward) to the mouse 60 inassociation with the predetermined movement of the mouse 60. Next, thecontrol section 91 controls (i) the operation of the movement of thehead plate latch 50 to release the head plate 60 a from a fixed stateand (ii) the operation of the opening of the automatic gates 80 a and 80b relative to the operation (i) so that the mouse 60 can move back tothe home cage 10. By carrying out such control once or preferablyrepeatedly with respect to an identical mouse 60, it is possible tocause the mouse 60 to learn that, by making the predetermined movement,for example, rotating the steering wheel 71, the mouse 60 can obtainwater from the water supply unit 72. In a case where a plurality of mice60 are kept in the home cage 10, it is possible to automatically andsimultaneously carry out learning training with respect to the pluralityof mice 60.

In addition, data on the activity of the mouse 60 restrained by the headplate latch 50 can be obtained with use of the activity data measuringdevice 51. Such activity data is preferably obtained from the mouse 60which has been subjected to the learning training.

That is, according to Aspect 3, the control section 91 automaticallycontrols the operation of the opening and the closing of the automaticgate 80, the water supply operation of the water supply unit 72,measurement operation of the activity data measuring device 51, and thefixation and release operation of the head plate latch 50 in accordancewith (i) the information on the position of the mouse 60, the data ofwhich position is obtained from each output of the plurality of beamsensors 22, (ii) an output of the steering wheel 71 (output resultingfrom rotation of the steering wheel 71 which rotation is caused by themouse 60), or (iii) the information on a interrelationship betweenoperation of one device and operation of another device (for example,between the operation of the head plate latch 50 and the operation ofeach of the automatic gates 80 a and 80 b, between the operation of thewater supply unit 72 and the operation of the steering wheel 71, betweenthe operation of the head plate latch 50 and the operation of theactivity data measuring device 51, and the like).

Note that a mouse to be conducted to the learning training can beautomatically selected by a weight of the mouse with use of the methoddescribed in <Aspect 1>.

(Variation of Mouse Restraining System)

The mouse restraining system 100 can include, instead of the steeringwheel 71 illustrated in FIG. 1, another device which receives themovement of the mouse 60.

Further, a reward/attractant supply unit which supplies a mouse withfeed or the like as a reward or an attractant can be used instead of thewater supply unit 72 illustrated in FIG. 1. In a case that the mouse isfed, the reward/attractant supply unit serves as a feeding unit. In thiscase, the above mentioned movement receiving device and thereward/attractant supply unit constitutes the learning device 70 for amouse.

The mouse restraining system 100 can be configured such that (i) thecontrol section 91 illustrated in FIG. 1 is omitted or a range ofautomatic control carried out by the control section 91 is limited and(ii) at least part of the devices constituting the mouse restrainingsystem 100 is manually operated. Even with this configuration, since thehome cage 10 is connected to the passage 20, to which the head platelatch 50 is provided, it is possible to relatively easily restrain themouse 60 with use of the head plate latch 50 while suppressing the humaninteraction so as to reduce the mouse 60's fear. Note, however, that thecontrol section 91 preferably 1) automatically controls at least theoperation of the head plate latch 50 and/or the operation of theautomatic gate 80 in accordance with the information on the position ofthe mouse 60, the data of which position is obtained from each output ofthe plurality of beam sensors 22, or 2) automatically controls at leastthe operation of the activity data measuring device 51 and/or theoperation of the learning device 70, each of which operation is carriedout with respect to the mouse 60 restrained by the head plate latch 50.This is because it is possible to further suppress the humaninteraction, thereby improving work efficiency and further reducing themouse 60's fear.

Note that, in consideration of only a purpose of causing the mouse 60 tobecome used to fixation by the head plate latch 50, the mouserestraining system 100 only needs to include at least the home cage 10,the passage 20, and the head plate latch 50 out of the devicesillustrated in FIG. 1, and the other devices are not essential.

Embodiment 2

The following description will discuss, with reference to FIG. 2, amouse restraining system in accordance with another embodiment of thepresent invention. Note that identical reference numerals will be givento members identical to those illustrated in FIG. 1, and the memberswill not be explained here.

A mouse restraining system 200 illustrated in FIG. 2 is different fromthe mouse restraining system 100 illustrated in FIG. 1 in innerstructure of a latch-side passage 20 c. In particular, the mouserestraining system 200 includes a habituation unit 23 (guide section forguiding a head plate) which comprises plate-shaped components attachedon respective internal side surfaces of the latch-side passage 20 c.Each of the plate-shaped components has an inclined part (guide rail) 23a which is inclined downward as extending from its home-cage-10 side toits head-plate-latch-50 side.

The habituation unit 23 functions as a guide section which increasescontrol on upward movement of a mouse 60 in stages (gradually reduces adegree of freedom of the upward movement of the mouse 60) as a headplate 60 a with which the mouse 60 is equipped comes into contact withthe inclined part 23 a and the mouse 60 becomes closer to a head platelatch 50. Note, however, that the habituation unit 23 does not preventthe mouse 60 from accessing the head plate latch 50, a water supply unit72, and a steering wheel 71. This makes it possible to (i) more easilyrestrain the mouse 60 with use of the head plate latch 50 whilesuppressing a rapid increase in mouse 60's fear or (ii) more easilycause the mouse 60 to become used to fixation by the head plate latch50.

(Variation of Habituation Unit)

A habituation unit 23′ illustrated in FIG. 3 can be used instead of thehabituation unit 23 illustrated in FIG. 2. The habituation unit 23′ hasplate-shaped components attached on the respective internal sidesurfaces of the latch-side passage 20 c. Each of the plate-shapedcomponents has (i) an inclined part (guide rail) 23 a′ which is inclineddownward as extending from its home-cage-10 side to itshead-plate-latch-50 side and (ii) an inclined part (guide rail) 23 b′which is inclined upward as extending from its home-cage-10 side to itshead-plate-latch-50 side. On the head-plate-latch-50 side, the inclinedparts 23 a′ and 23 b′ form a parallel part 23 c′ (restraining groove) byextending in parallel toward the head plate latch 50 while havingtherebetween a predetermined gap with which the head plate 60 a isengaged (for example, a space which is slightly larger than a thicknessof the head plate 60 a). An end of the parallel part 23 c′ located onits head-plate-latch-50 side is closed. That is, the inclined part 23 a′and the inclined part 23 b′ constitute a substantially Y-shaped guidesection, and increase control on upward and downward movement of themouse 60 in stages as the head plate 60 a with which the mouse 60 isequipped comes into contact with the inclined part 23 a′ and theinclined part 23 b′ and the mouse 60 becomes closer to the head platelatch 50. In a case where the head plate 60 a is engaged with theparallel part 23 c′, the mouse 60 cannot substantially move upward ordownward. However, such engagement does not prevent the mouse 60 fromaccessing the water supply unit 72 and the steering wheel 71. In such astate, since a rapid increase in mouse 60's fear is suppressed, it ispossible to more easily restrain the mouse 60 with use of the head platelatch 50.

Here, the head plate latch 50 includes a first latching bar 50 a and asecond latching bar 50 b. The first and the second latching bars 50 aand 50 b are provided so that a lower end of each of the first and thesecond latching bars 50 a and 50 b is located in the parallel part 23 c′of the habituation unit 23′, when viewed from a direction of a sidesurface of a passage 20. The first latching bar 50 a is provided on anupstream side (home-cage-10 side) of the passage 20, and the secondlatching bar 50 b is provided slightly downstream from the firstlatching bar 50 a so that the first and the second latching bars 50 aand 50 b are spaced out. In a case where the mouse 60 moves forward, thehead plate 60 a comes into contact with the lower end of the firstlatching bar 50 a so that the first latching bar 50 a is pushed up. Thefirst latching bar 50 a goes back down (by gravity) as the mouse 60keeps on moving forward. In a case where the first latching bar 50 agoes back down, the first latching bar 50 a comes into contact with aside surface of the head plate 60 a which side surface is located on arear side of the head plate 60 a. This causes the head plate 60 a to befixed so that the mouse 60 cannot move back. In a case where the mouse60 further moves forward, the second latching bar 50 b is pushed up andthen goes back down, as with the case of the first latching bar 50 a. Asa result, the second latching bar 50 b restrains the head plate 60 a tothe very end of the parallel part 23 c′ (narrowing guide rails), whereno degrees of freedom are allowed, of the habituation unit 23′. At theend of a training session, a servo-motor mechanism (not illustrated)lifts up both the first and the second latching bars 50 a and 50 b tolet the mouse 60 return to the home cage 10. This dual latching systemis one of keys to quickly train a mouse to self-head-latch: a mouse,after passing the first latching bar 50 a, although fairly restrained bythe habituation unit 23′ (guide section), can still move its head andbody, which greatly reduces its stress level.

Note that the habituation unit 23′ illustrated in FIG. 3 can beconfigured so as not to have the inclined part 23 a′ and so as toinclude merely the inclined part 23 b′. This also makes it possible toincrease control on downward movement of the mouse 60 in stages as thehead plate 60 a with which the mouse 60 is equipped comes into contactwith the inclined part 23 b′ and the mouse 60 becomes closer to the headplate latch 50.

Embodiment 3

The mouse restraining system illustrated in each of FIGS. 1 through 3can be configured such that: 1) a plurality of home cages 10 areprovided therein; 2) a passage 20 having a plurality of open ends 21 a(first open ends) the number of which is identical to that of theplurality of home cages 10 (for example, a passage 20 whose one end isbranched depending on the number of the plurality of home cages 10) orpassages 20 the number of which is identical to that of the plurality ofhome cages 10 is/are provided therein; and 3) such plurality of openends 21 a are connected to the respective plurality of home cages 10.

This allows an increase in number of mice 60 which can be introduced toa head plate latch 50, in proportion to the number of the plurality ofhome cages 10. It is therefore possible to achieve a high throughputexperiment.

For example, (A) of FIG. 4 schematically illustrates a configuration ofa mouse restraining system 300 including: n (n is an integer of 2 ormore) home cages 10 (in (A) of FIG. 4, three home cages 10 areprovided); a passage 20 branched so as to have n open ends 21 a on itsrespective home-cage-10 sides; and a single common head plate latch 50.A side of the passage 20 on which side the head plate latch 50 isprovided is not branched, and the passage 20 has a single open end 21 b.The mouse restraining system 300 includes automatic gates 80 c inaddiction to automatic gates 80 a and 80 b (see also FIGS. 1 and 2). Theautomatic gates 80 c are provided in respective regions that are locatedon respective parts of the passage 20 which parts extend from abranching point 20 d of the passage 20 to the respective open ends 21 aand that are located in respective vicinities of the branching point 20d. Opening and closing of the automatic gates 80 c are controlled asfollows. That is, for example, one of the automatic gates 80 c iscontrolled to be opened, while the other ones of the automatic gates 80c are controlled to be closed, so that a mouse 60 can move to the headplate latch 50 merely from a selected one of the home cages 10.

(B) of FIG. 4 schematically illustrates a configuration of a mouserestraining system 400 including: n (n is an integer of 2 or more) homecages 10 (in (B) of FIG. 4, four home cages 10 are provided); n passages20; and a single common head plate latch 50. Open ends 21 a of thepassages 20 are connected to the respective different home cages 10 andall of open ends 21 b of the passages 20 are connected to the commonhead plate latch 50. Opening and closing of a plurality of automaticgates 80 are controlled so that a mouse 60 is sent to the head platelatch 50 merely from a selected one of the home cages 10.

Note that, in FIG. 4, identical reference numerals are given to membersidentical to those illustrated in FIGS. 1 and 2 and the members will notbe explained here.

The present invention is not limited to the embodiments, but can bealtered by a skilled person in the art within the scope of the claims.An embodiment derived from a proper combination of technical means eachdisclosed in a different embodiment is also encompassed in the technicalscope of the present invention.

EXAMPLES

Hereinafter, the present invention will be described more specificallyby way of Examples, but the scope of the present invention is notintended to be limited to the following Examples

[Example 1] Physiological Recording and Brain Imaging from a Head-FixedMouse Trained in the Invented Setup

A system for measuring activities of a CaMKII-cre:LSL-GCaMP3 mouse wasset up. The system includes a fluorescence macroscope, an eye-trackingcamera, an LCD display to present visual stimuli to the animal, ahead-latching stage identical to that of the training system illustratedin FIG. 3. The mouse was kept and trained at the system. First, a dorsalcortex of a transgenic mouse was monitored to obtain a fluorescent imageof chronic wide-field (FIG. 5(A), Red lines, contours of 8 visual areasincluding a primary visual cortex, V1).

At the same time as the dorsal cortex was imaged, a contra-lateral eyewas imaged as well at high magnification under infra-red illumination.In this specific experiment, fluorescent signals, which reflected neuralactivations, were acquired as stimuli were presented on a screen placedin front of the animal. The task was to discriminate two visual stimuli,hence it was critical to control for eye movements. The trained animalperformed at ˜80% correct rate. Eye images were processed by anautomated-segmentation algorithm which identified eye contours (greenoval) and pupil (yellow circle) (FIG. 5(B)).

Horizontal pupil displacement calculated from FIG. 5(B) is shown inarbitrary pixel units (black line, left y-axis) together withfluorescent activations from V1 (blue line, right y-axis). Verticaldotted lines, time interval during which the animal could form adecision, but could not signal it. After t=2.5 s the animal could signalhis choice via forepaws movements on a mechanical actuators (FIG. 5(C)).Temporal evolution of a pupil diameter (arbitrary pixel units)calculated using the segmentation algorithm, as shown in FIG. 5 (B),plotted on the same temporal axis as the neural recordings (FIG. 5(D)).

REFERENCE SIGNS LIST

-   home cage 10-   passage 20-   cage-side passage 20 a-   middle passage 20 b-   latch-side passage 20 c-   open end 21 a-   open end 21 b-   beam sensor 22-   beam sensor 22 a-   beam sensor 22 b-   beam sensor 22 c-   branching point 20 d-   habituation unit 23-   inclined part 23 a-   habituation unit 23′-   inclined part 23 a′-   inclined par 23 b′-   parallel part 23 c′ (restraining groove)-   head plate latch (restraining device) 50-   first latching bar 50 a-   second latching bar 50 b-   activity data measuring device 51-   mouse 60-   head plate 60 a-   through window 60 a ₁-   recesses 60 a ₂ and 60 a ₂-   learning device 70-   steering wheel 71-   water supply unit 72-   automatic gate 80-   automatic gates (door) 80 a and 80 b-   automatic gates 80 c-   weight sensor 90-   control section 91-   mouse restraining system 100-   mouse restraining system 200-   mouse restraining system 300-   mouse restraining system 400

1. A system for restraining a mouse, comprising: at least one home cagefor keeping the mouse therein; a passage through which the mouse moves,the passage having at least one first open end; and a restraining devicewhich restrains the mouse by physically fixing the mouse, the at leastone first open end of the passage being connected to the at least onehome cage, the restraining device being provided at a location on thepassage which location is different from the at least one first open endof the passage.
 2. The system as set forth in claim 1, wherein therestraining device restrains the mouse by physically fixing a head platewith which the head of the mouse is equipped.
 3. The system as forth inclaim 2, further comprising a guide section which guides the head plate,the guide section being provided to the passage and having a partinclined upward or downward as extending toward the restraining device.4. The system as set forth in claim 1, wherein: the passage has a secondopen end which is different from the at least one first open end; andthe restraining device is provided on a second-open-end side of thepassage.
 5. The system as set forth in claim 1, further comprising adoor which can be opened and closed, the door dividing an inner space ofthe passage into a first-open-end-side space and arestraining-device-side space in a case where the door is closed.
 6. Thesystem as set forth in claim 1, further comprising a sensor whichdetects a position of the mouse being inside the passage.
 7. The systemas set forth in claim 6, wherein operation of the restraining deviceand/or operation of a/the door are/is automatically controlled inaccordance with information on the position of the mouse, data of whichposition is obtained from an output of the sensor.
 8. The system as setforth in claim 1, further comprising an activity data measuring devicewhich obtains data on activity of the mouse restrained by therestraining device.
 9. The system as set forth in claim 1, furthercomprising a learning device which supplies a reward to the mouse inassociation with predetermined movement of the mouse restrained by therestraining device.
 10. The system as set forth in claim 8, furthercomprising a control section which automatically controls operation ofan/the activity data measuring device and/or operation of a/the learningdevice each of which operation is carried out with respect to the mouserestrained by the restraining device.
 11. The system as set forth inclaim 1, wherein: the at least one first open end of the passageincludes a plurality of first open ends; the at least one home cageincludes a plurality of home cages; and the plurality of first open endsare connected to the respective plurality of home cages.